Agricultural planting system with automatic depth control

ABSTRACT

A control system for controlling the depth of an opener device in an agricultural planter comprises a gauge wheel on a pivotably mounted support arm, a mechanical element coupled to the support arm to move in response to changes in the angle of the support arm, a sensor adapted to measure changes in the relative elevations of the opener device and the gauge wheel to produce an output signal representing the current relative elevations of the opener device and the gauge wheel, and a control device receiving the output signal from the sensor and producing a second output signal for maintaining the opener device at a selected elevation relative to the gauge wheel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. application Ser. No.15/637,692, filed Jun. 29, 2017, U.S. application Ser. No. 14/858,089,filed Sep. 18, 2015, U.S. Provisional Application No. 62/085,334, filedNov. 28, 2014, and U.S. Provisional Application No. 62/076,767, filedNov. 7, 2014, each of which is hereby incorporated by reference hereinin its entirety.

U.S. patent application Ser. No. 14/593,492, filed Jan. 9, 2015;

U.S. patent application Ser. No. 14/858,171, filed Sep. 18, 2015;

U.S. patent application Ser. No. 15/586,743, filed May 4, 2017; and

U.S. patent application Ser. No. 15/586,799, filed May 4, 2017.

FIELD OF THE INVENTION

This invention relates generally to agricultural planters and, moreparticularly, to gauge wheel load sensors and down pressure controlsystems for agricultural planters.

BRIEF SUMMARY

In accordance with one embodiment, a control system for controlling thedepth of an opener device in an agricultural planter comprises a gaugewheel on a pivotably mounted support arm, a mechanical element coupledto the support arm to move in response to changes in the angle of thesupport arm, a sensor adapted to measure changes in the relativeelevations of the opener device and the gauge wheel to produce an outputsignal representing the current relative elevations of the opener deviceand the gauge wheel, and a control device receiving the output signalfrom the sensor and producing a second output signal for maintaining theopener device at a selected elevation relative to the gauge wheel.

One implementation includes a moisture sensor producing a signalrepresenting the moisture content of the soil being planted, and thecontrol device is responsive to the moisture-representing signal forproducing an output signal representing the desired depth of the openingdevice.

The sensor may translate the upward force from a pivoting gauge wheelsupport arm into a fluid pressure in a fluid chamber, and a pressuretransducer may be coupled to the fluid chamber and produce an outputsignal that changes in proportion to changes in the fluid pressure inthe fluid chamber. The control device may receive the output signal anduse that output signal to produce a second output signal for maintainingsaid opener device at a selected elevation relative to said gauge wheel.

In one implementation, the control device supplies a control signal to arelief valve to open the relief valve in response to a predeterminedchange in the pressure of the pressurized fluid and also supplies acontrol signal to a variable orifice to control the size of the orificewhen the relief valve is open, to control the rate of flow ofpressurized fluid to the fluid chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical longitudinal section through a portion of anagricultural planter that includes a gauge wheel and an opener device.

FIG. 2 is an enlargement of the left side of FIG. 1.

FIG. 3 is a bottom perspective of the control portion of the equipmentshown in FIG. 1.

FIG. 4 is an enlarged side elevation of the equipment shown in FIG. 3.

FIG. 5 is an enlarged top plan view of the equipment shown in FIG. 3.

FIG. 6 is an enlarged vertical longitudinal section through theequipment shown in FIG. 3.

FIG. 7 is a schematic diagram of a hydraulic control system forcontrolling the hydraulic system using a gauge wheel load sensor.

FIG. 8 is a schematic diagram of a modified hydraulic control system forcontrolling the hydraulic system using a gauge wheel load sensor.

FIG. 9 is a waveform diagram illustrating different modes of operationprovided by the hydraulic control systems of FIGS. 7 and 8.

FIG. 10 is a plan view of a gauge wheel transducer system for anagricultural planter that includes a gauge wheel and an opener device.

FIG. 11 is a side elevation of the transducer system shown in FIG. 10.

FIG. 12 is a sectional view taken along line A-A in FIG. 10.

FIG. 13 is a side elevation, partially in section, of the transducersystem of FIGS. 10-12 mounted on a gauge wheel and its supportingstructure.

FIG. 14 is a perspective view of portions of the devices shown in FIG.13.

FIG. 15 is a plan view similar to FIG. 10 but with portions removed toshow the equalizer arm.

FIG. 16 is a plan view of a modified transducer system.

FIG. 17 is a longitudinal section taken along line 17-17 in FIG. 16.

FIG. 18A is a side elevation of a modified sensing system for detectingthe pressure exerted on a pair of gauge wheels.

FIG. 18B is an end elevation of the system shown in FIG. 18A.

FIG. 19 is a schematic diagram of a hydraulic and electrical controlsystem for controlling a down pressure actuator.

FIG. 20 is a schematic diagram of a first modified hydraulic andelectrical control system for controlling a down pressure actuator.

FIG. 21 is a schematic diagram of a second modified hydraulic andelectrical control system for controlling a down pressure actuator.

FIG. 22 is a schematic diagram of a third modified hydraulic andelectrical control system for controlling a down pressure actuator.

FIG. 23 is a schematic diagram of a fourth modified hydraulic andelectrical control system for controlling a down pressure actuator.

FIG. 24 is a flow chart of an exemplary algorithm executed by thecontroller in the system of FIG. 23.

FIG. 25 is a schematic diagram of a fifth modified hydraulic andelectrical control system for controlling a down pressure actuator.

FIG. 26 is sectional elevation of a modified embodiment of an automaticdepth control system.

FIG. 27 is a reduced version of the control system of FIG. 26 positionedadjacent a gauge wheel and its support arm.

FIG. 28 is a perspective view of the gauge wheel and control systemshown in FIG. 27

FIG. 29 is an enlarged top plan view of the gauge wheel and controlsystem shown in FIG. 28.

FIG. 30 is a side elevation of the control system shown in FIG. 26.

FIG. 31 is an enlarged section taken along line 31-31 in FIG. 30.

FIG. 32 is an enlarged section taken along line 32-32 in FIG. 30.

FIG. 33 is an enlarged view of the slider/depth adjuster in the controlsystem of FIG. 30, with the slider/depth adjuster in two differentpositions.

FIG. 34 is a flow chart of an algorithm for use in the control system ofFIGS. 26-33.

DETAILED DESCRIPTION

An agricultural planter typically includes a number of individual rowunits, each of which includes its own row cleaner device, row openerdevice and row closing device. The down pressure is typically controlledseparately for each row unit or each of several groups of row units, andis preferably controlled separately for one or more of the individualdevices in each row unit, as described in more detail in pending U.S.application Ser. No. 14/146,822 filed Jan. 3, 2014, which isincorporated by reference herein in its entirety.

FIGS. 1-6 illustrate an improved gauge wheel load sensor that takes theupward force from a pivoting planter gauge wheel support, such as thepivoting support arms 10 in the row unit equipment shown in FIGS. 1 and2, and translates that force into a fluid pressure in a fluid chamber11. The gauge wheel support arms push against an equalizer support 12,which is connected via a pivot 13 with a rocker/cam 14. The force on thegauge wheel due to the weight of the row unit and applied down forcecauses the rocker/cam 14 to pivot around a pivot bolt 15 and pushagainst a hydraulic ram 16. This force on the ram 16 causes the fluid inthe chamber 11 to pressurize. The pressure is proportional to the amountof gauge wheel load. A pressure transducer 18 reads the amount ofpressure and sends a signal to a row unit down pressure controller viasignal line 19. This signal allows the planter row unit down pressure tobe controlled to a desired level.

Depth adjustment is accomplished in the conventional sense by pivotingthe assembly around a pivot 20, and locking a handle 21 into the desiredposition with a mechanism 22. With this design it is preferred that thatthere is no air trapped in the fluid chamber 11. For this reason themechanism includes a bleed valve 23. The process for removal of air isto extend the ram to the maximum extent with calibration/travel limiterplates 24 (FIG. 4) removed. The system is then filled completely withfluid with the bleed valve 23 closed. Then the bleed valve 23 is opened,and the rocker arm 14 is pushed against the ram 16 to move the ram tothe exact place where the calibration/travel limit plates 24 allow acalibration plate retaining screw 25 to fit into a hole. This ensuresthat each assembly is set the same so all the row units of the planterare at the same depth. At this point the bleed valve 23 is closed. Withall air removed, the mechanical/fluid system will act as a rigid memberagainst forces in compression. The travel limiter plate 24 keeps a campivot weldment from falling down when the planter is lifted off theground.

Standard industry practice is to use a strain gauge to directly measurethe planter gauge wheel load. The design shown in FIGS. 1-6 is animprovement over the state of the art because it allows the sensor tomeasure only the down force on the gauge wheels. In typical designsusing strain gauge type sensors, the mechanical linkage that allows thegauge wheels to oscillate causes the measured wheel force to havesubstantial noise due to changes in the force being applied. For thisreason it can be difficult to determine which parts of the signalcorrespond to actual changes in down force on the gauge wheels, versussignal changes that are due to movement of components of the gauge wheelsupport mechanism. The reason for this is that strain gauge sensors willonly measure the force that is being applied in a single plane. Becauseof the linkage and pivot assembly that is used on typical planters, theforce being applied to the strain gauge type designs can change based onthe depth setting or whether the planter gauge wheels are oscillatingover terrain. In this way they will tend to falsely register changes ingauge wheel down force and make it difficult to have a closed loop downpressure response remain consistent.

The fluid seal of the pressure sensor described here creates friction inthe system which has the effect of damping out high frequency noise.Agricultural fields have very small scale variations in the surfacewhich cause noise to be produced in the typical down force sensorapparatus. By using fluid pressure this invention decouples the sensorfrom the mechanical linkage and allows the true gauge wheel force to bemore accurately measured. Lowering the amount of systematic noise in thegauge wheel load output sensor makes it easier to produce an automaticcontrol system that accurately responds to true changes in the hardnessof the soil, as opposed to perceived changes in soil hardness due tonoise induced on the sensor.

FIG. 7 is a schematic diagram of a hydraulic control system for any orall of the hydraulic actuators in a down pressure control system. Thehydraulic cylinder 2600 is supplied with pressurized hydraulic fluidfrom a source 2601 via a first controllable two-position control valve2602, a restriction 2603 and a check valve 2604. The pressurizedhydraulic fluid supplied to the cylinder 2600 can be returned from thecylinder to a sump 2605 via a second controllable two-position controlvalve 2606, a restriction 2607 and a check valve 2608. Both the controlvalves 2602 and 2606 are normally closed, but can be opened byenergizing respective actuators 2609 and 2610, such as solenoids.Electrical signals for energizing the actuators 2609 and 2610 aresupplied to the respective actuators via lines 2611 and 2612 from acontroller 2613, which in turn may be controlled by a central processor2614. The controller 2613 receives input signals from a plurality ofsensors, which in the example of FIG. 7 includes a pressure transducer2615 coupled to the hydraulic cylinder 2600 via line 2616, and a groundhardness sensor 2617. An accumulator 2618 is also coupled to thehydraulic cylinder 2600, and a relief valve 2619 connects the hydrauliccylinder 2600 to the sump 2605 in response to an increase in thepressure in the cylinder 2600 above a predetermined level.

To reduce the energy required from the limited energy source(s)available from the tractor or other propulsion device used to transportthe row units over an agricultural field, the control valves 2602 and2606 are preferably controlled with a pulse width modulation (PWM)control system implemented in the controller 2613. The PWM controlsystem supplies short-duration (e.g., in the range of 50 milliseconds to2 seconds with orifice sizes in the range of 0.020 to 0.2 inch) pulsesto the actuators 2609 and 2610 of the respective control valves 2602 and2606 to open the respective valves for short intervals corresponding tothe widths of the PWM pulses. This significantly reduces the energyrequired to increase or decrease the pressure in the hydraulic cylinder2600. The pressure on the exit side of the control valve is determinedby the widths of the individual pulses and the number of pulses suppliedto the control valves 2602 and 2606. Thus, the pressure applied to thehydraulic cylinder 2622 may be controlled by separately adjusting thetwo control valves 2602 and 2606 by changing the width and/or thefrequency of the electrical pulses supplied to the respective actuators2609 and 2610, by the controller 2613. This avoids the need for aconstant supply current, which is a significant advantage when the onlyavailable power source is located on the tractor or other vehicle thatpropels the soil-engaging implement(s) across a field.

The hydraulic control system of FIG. 7 may be used to control multiplehydraulic cylinders on a single row unit or a group of row units, or maybe replicated for each individual hydraulic cylinder on a row unithaving multiple hydraulic cylinders. For example, in the systemdescribed above having a ground hardness sensor located out in front ofthe clearing wheels, it is desirable to have each hydraulic cylinder onany given row unit separately controlled so that the down pressure oneach tool can be adjusted according to the location of that tool in thedirection of travel. Thus, when the ground hardness sensor detects aregion where the soil is softer because it is wet, the down pressure oneach tool is preferably adjusted to accommodate the softer soil onlyduring the time interval when that particular tool is traversing the wetarea, and this time interval is different for each tool when the toolsare spaced from each other in the direction of travel. In the case of agroup of row units having multiple hydraulic cylinders on each row unit,the same hydraulic control system may control a group of valves havingcommon functions on all the row units in a group.

FIG. 8 is a schematic diagram of a modified hydraulic control systemthat uses a single three-position control valve 2620 in place of the twotwo-position control valves and the two check valves used in the systemof FIG. 7. The centered position of the valve 2620 is the closedposition, which is the normal position of this valve. The valve 2620 hastwo actuators 2620 a and 2620 b, one of which moves the valve to a firstopen position that connects a source 2621 of pressurized hydraulic fluidto a hydraulic cylinder 2622 via restriction 2620 c, and the other ofwhich moves the valve to a second open position that connects thehydraulic cylinder 2622 to a sump 2623. Electrical signals forenergizing the actuators 2620 a and 2620 b are supplied to therespective actuators via lines 2624 and 2625 from a controller 2626,which in turn may be controlled by a central processor 2627. Thecontroller 2626 receives input signals from a pressure transducer 2628coupled to the hydraulic cylinder 2622 via line 2629, and from anauxiliary sensor 2630, such as a ground hardness sensor. An accumulator2631 is coupled to the hydraulic cylinder 2622, and a relief valve 2632connects the hydraulic cylinder 2622 to the sump 2623 in response to anincrease in the pressure in the cylinder 2622 above a predeterminedlevel.

As depicted in FIG. 9, a PWM control system supplies short-durationpulses P to the actuators 2620 a and 2620 b of the control valve 2620 tomove the valve to either of its two open positions for short intervalscorresponding to the widths of the PWM pulses. This significantlyreduces the energy required to increase or decrease the pressure in thehydraulic cylinder 2622. In FIG. 9, pulses P1-P3, having a voltage levelV1, are supplied to the actuator 2620 b when it is desired to increasethe hydraulic pressure supplied to the hydraulic cylinder 2622. Thefirst pulse P1 has a width T1 which is shorter than the width of pulsesP2 and P3, so that the pressure increase is smaller than the increasethat would be produced if P1 had the same width as pulses P2 and P3.Pulses P4-P6, which have a voltage level V2, are supplied to theactuator 2620 a when it is desired to decrease the hydraulic pressuresupplied to the hydraulic cylinder 2622. The first pulse P4 has a widththat is shorter than the width T2 of pulses P2 and P3, so that thepressure decrease is smaller than the decrease that would be produced ifP4 had the same width as pulses P5 and P6. When no pulses are suppliedto either of the two actuators 2620 a and 2620 b, as in the “no change”interval in FIG. 9, the hydraulic pressure remains substantiallyconstant in the hydraulic cylinder 2622.

FIGS. 10-15 illustrate a modified gauge wheel load sensor that includesan integrated accumulator 122. The purpose of the accumulator 122 is todamp pressure spikes in the sensor when the planter is operating at lowgauge wheel loads. When the forces that the gauge wheel support arms 110are exerting on the hydraulic ram 117 are near zero, it is more commonfor the surface of the soil or plant residue to create pressure spikesthat are large in relation to the desired system sensor pressure. Thesepressure spikes produce corresponding changes in the vertical position(elevation) of the gauge wheels. As the target gauge wheel down forceincreases, and consequently the pressure in the fluid chamber 111, whichis coupled to a bleed valve 123, and the transducer output voltage fromsensor 118, the small spikes of pressure due to variations in the soilsurface or plant residue decrease proportionally.

In the present system, rather than have a perfectly rigid fluid couplingbetween the ram 117 and the pressure transducer 118, as load increaseson the ram 117, the fluid first pushes against a piston 125 of theaccumulator 122 that is threaded into a side cavity 123 in the samehousing that forms the main cavity for the ram 117. The increasedpressure compresses an accumulator spring 126 until the piston 125 restsfully against a shoulder on the interior wall of the accumulator housing127, thus limiting the retracting movement of the accumulator piston125. At this point, the system becomes perfectly rigid. The amount ofmotion permitted for the accumulator piston 125 must be very small sothat it does not allow the depth of the gauge wheel setting to fluctuatesubstantially. The piston accumulator (or other energy storage device)allows the amount of high frequency noise in the system to be reduced atlow gauge-wheel loads. Ideally an automatic down pressure control systemfor an agricultural planter should maintain a down pressure that is aslow as possible to avoid over compaction of soil around the area of theseed, which can inhibit plant growth. However, the performance of mostsystems degrades as the gauge wheel load becomes close to zero, becausethe amount of latent noise produced from variation in the field surfaceis large in relation to the desired gauge wheel load.

Planter row units typically have a gauge wheel equalizer arm 130 that isa single unitary piece. It has been observed that the friction betweenthe equalizer arm 130 and the gauge wheel support arms 110, as the gaugewheel 115 oscillates up and down, can generate a substantial amount ofnoise in the sensor. At different adjustment positions, the edges of theequalizer arm 130 contact the support arms 10 at different orientationsand can bite into the surface and prevent forces from being smoothlytransferred as they increase and decrease. When the equalizer arm 130 isa single unitary piece, there is necessarily a high amount of frictionthat manifests itself as signal noise in the sensor. This signal noisemakes it difficult to control the down pressure system, especially atlow levels of gauge wheel load.

To alleviate this situation, the equalizer arm 130 illustrated in FIG.16 has a pair of contact rollers 131 and 132 are mounted on oppositeends of the equalizer arm. These rollers 131 and 132 become theinterface between the equalizer arm and the support arms 110, allowingforces to be smoothly transferred between the support arms 110 and theequalizer arm 130. The roller system allows the gauge wheel support arms110 to oscillate relative to each other without producing any slidingfriction between the support arms 110 and the equalizer arm 130. Thissignificantly reduces the friction that manifests itself as signal noisein the sensor output, which makes it difficult to control the downpressure control system, especially at low levels of gauge wheel load.

FIG. 17 is a longitudinal section through the device of FIG. 16, withthe addition of a rocker arm 150 that engages a ram 151 that controlsthe fluid pressure within a cylinder 152. A fluid chamber 153 adjacentthe inner end of the ram 151 opens into a lateral cavity that contains apressure transducer 154 that produces an electrical output signalrepresenting the magnitude of the fluid pressure in the fluid chamber153. The opposite end of the cylinder 152 includes an accumulator 155similar to the accumulator 122 included in the device of FIG. 12described above. Between the fluid chamber 153 and the accumulator 155,a pair of valves 156 and 157 are provided in parallel passages 158 and159 extending between the chamber 153 and the accumulator 155. The valve156 is a relief valve that allows the pressurized fluid to flow from thechamber 153 to the accumulator 155 when the ram 151 advances fartherinto the chamber 153. The valve 157 is a check valve that allowspressurized fluid to flow from the accumulator 155 to the chamber 153when the ram 151 moves outwardly to enlarge the chamber 153. The valves156 and 157 provide overload protection (e.g., when one of the gaugewheels hits a rock) and to ensure that the gauge wheels retain theirelevation setting.

FIGS. 18A and 18B illustrate a modified sensor arrangement for a pair ofgauge wheels 160 and 161 rolling on opposite sides of a furrow 162. Thetwo gauge wheels are independently mounted on support arms 163 and 164connected to respective rams 165 and 166 that control the fluid pressurein a pair of cylinders 167 and 168. A hydraulic hose 169 connects thefluid chambers of the respective cylinders 167 and 168 to each other andto a common pressure transducer 170, which produces an electrical outputsignal corresponding to the fluid pressure in the hose 169. The outputsignal is supplied to an electrical controller that uses that signal tocontrol the down forces applied to the two gauge wheels 160 and 161. Itwill be noted that the two gauge wheels can move up and downindependently of each other, so the fluid pressure sensed by thetransducer 170 will be changed by vertical movement of either or both ofthe gauge wheels 160 and 161.

FIGS. 19-22 illustrate electrical/hydraulic control systems that can beused to control a down-pressure actuator 180 in response to theelectrical signal provided to a controller 181 by a pressure transducer182. In each system the transducer 182 produces an output signal thatchanges in proportion to changes in the fluid pressure in a cylinder 183as the position of a ram 184 changes inside the cylinder 183. In FIG.19, the pressurized fluid chamber in the cylinder 183 is coupled to anaccumulator 185 by a relief valve 186 to allow pressurized fluid to flowto the accumulator, and by a check valve 187 to allow return flow ofpressurized fluid from the accumulator to the cylinder 183. In FIG. 20,the accumulator 185 is replaced with a pressurized fluid source 188connected to the check valve 187, and a sump 189 connected to the reliefvalve 186. In FIG. 21, the accumulator 185 is connected directly to thepressurized fluid chamber in the cylinder 183, without any interveningvalves. In the system of FIG. 22, there is no accumulator, and thepressure sensor 182 is connected directly to the pressurized fluidchamber in the cylinder 183.

FIG. 23 illustrates a modified electrical/hydraulic control system forcontrolling a down-pressure actuator 200 in response to an electricalsignal provided to a controller 201 by a pressure transducer 202. Thetransducer 202 produces an output signal that changes in proportion tochanges in the fluid pressure in a cylinder 203 as the position of a ram204 changes inside the cylinder 203. Thus the ram 204 functions as agauge wheel sensor. The pressurized fluid chamber in the cylinder 203 iscoupled to an accumulator 205 by a controllable valve 206 to allowpressurized fluid to flow to the accumulator 205 through a controllablevariable orifice 207, and by a check valve 208 to allow return flow ofpressurized fluid from the accumulator 205 to the cylinder 203.

When the force applied to the piston 204, e.g., by the rocker arm 14,increases when the ground-engaging implement encounters harder ground orstrikes a rock, the piston 204 is moved to the left. This causes aportion of the pressurized fluid to flow through the variable orifice207 and the relief valve 206 to the accumulator 205. Both the variableorifice 207 and the relief valve 206 are controlled by electricalcontrol signals from the controller 201, which receives the outputsignal from the pressure sensor 202.

The variable orifice 207 acts as an adjustable and controllable damperaffecting the stiffness of, for example, a planter gauge wheelsuspension. Also, the electro-proportional relief valve 206 allows thestiffness of, for example, a planter row unit ride to be changeddynamically. For example, the controller 201 can be programmed to allowa stiffer setting or higher relief pressure in smooth fields. In rougherfields, the relief pressure can be reduced to allow more travel of thegauge wheels relative to the opener disks. This results in less bouncingof the row unit. The amount of variation in the pressure sensor outputsignal reflects variations in the roughness of the field. The controllercan use this variation or smoothness of the pressure signal over time tocontrol the relief pressure in real time.

When the force applied to the piston is reduced, the fluid pressurewithin the cylinder 203 is reduced, and the accumulator causes a portionof the fluid to flow back into the cylinder 203 via the check valve 208.The reduced pressure is sensed by the pressure sensor 202, whichproduces a corresponding change in the sensor output signal supplied tothe controller 201.

The controller 201 is programmed with an algorithm represented by theflow chart in FIG. 24. The first step 250 selects a predetermined system“mapping” of variables such as the diameter of the variable orifice 207and relief pressure in the cylinder 203. Other variables such as thedown pressure control system set point can be included in the mapping.The mapping is based on tillage and soil conditions that lead to typicalcharacteristics in the sensor data. After the mapping of the selectedvariables, a field operation such as planting, fertilizing or tillage,is started at step 251, and at step 252 the pressure transducer 202supplies the controller 201 with a signal that varies with the fluidpressure in the cylinder 203, which corresponds to changes in the gaugewheel load. The controller 201 computes a running average value of thegauge wheel load for a selected time period at step 253, and at step 254supplies a control signal to the down-pressure actuator 200 to controlthe down pressure in a closed loop.

In parallel with the closed loop control of the down-pressure actuator200, the controller also adjusts the values of the mapped variables insteps 255-259. Step 255 performs a statistical analysis of the gaugewheel sensor values to determine the signal-to-noise ratio (“SNR”), ofthe level of the desired signal to the level of background noise in thegauge wheel down pressure signal. The SNR can be determined by any ofthe known standard procedures, such as determining the ratio of thearithmetic mean to the standard deviation. The controller thendetermines whether the current SNR is above or below a preselectedvalue, at steps 256 and 257. If the SNR is determined to be above thepreselected value at step 256, step 258 adjusts the mapped values toreduce the target set point and the orifice diameter and to increase therelief pressure. If the SNR is below the preselected value at step 257,step 259 adjusts the mapped values to increase the target set point andthe orifice diameter and to decrease the relief pressure.

FIG. 25 illustrates a modified control system in which the relief valve206 is replaced with a controllable 3-way valve 306, and a sump 309 anda pressure supply pump 310 are connected to the valve 306. This controlsystem also includes a position sensor 302, such as an inductive sensoror a linear encoder, which supplies the controller 301 with a signalrepresenting the position of the piston 304 within the cylinder 303. Thesignal from the position sensor 302 enables the controller 301 toidentify in real time the depth of the opener relative to the gaugewheel.

When the 3-way valve 306 is in its center position, as shown in FIG. 25,the cylinder 303 is disconnected from both the sump 309 and the pump310, and thus the cylinder 303 is coupled to the accumulator 305 via thevariable orifice 307. This is the normal operating position of the valve306. When the controller 301 produces a signal that moves the valve 306to the right, the valve connects the cylinder 303 to the pressure supplypump 310 to increase the fluid pressure in the cylinder 303 to a desiredlevel. When the controller 301 produces a signal that moves the valve306 to the left, the valve connects the cylinder 303 to the sump 309 torelieve excessive pressure in the cylinder 303.

The system in FIG. 25 allows active control of the depth of theground-engaging element by using the pressure control valve 306 tochange the pressure in the cylinder 303. Because the piston 304 isconnected to the gauge wheel arms via the rocker, the gauge wheels moverelative to the opener disks as the piston 304 moves in and out.

When planting an agricultural field with seeds, it is important tocontrol the planting depth in real time as the planting machinetraverses the field, because it is critical that the seeds all beplanted into moisture so that each seed emerges from the soil at thesame time. The depth of the seed can be changed based on some type ofmoisture sensor system, or even based on a satellite or drone systemthat is able to detect changes in the soil chemistry that would make itdesirable to change the depth of the planted seed in different areas ofthe field.

FIG. 26 illustrates a modified system that enables the operator toselect a desired planting depth setting, and then automaticallymaintains the actual planting depth within a selected range above andbelow the selected depth. In this system, a fluid chamber 408 includes afluid port 420 (see FIGS. 30 and 31) that is connected to one or morevalves to allow hydraulic fluid to be added to or removed from thechamber 408 to change the angle of the opener disc relative to the gaugewheel. A distance sensor 411 produces an output signal representing theposition of the opener disc support arm along the arcuate guide, whichchanges as the angle between the two support arm changes with changes inthe depth of the opener disc relative to the elevation of the gaugewheel (the soil surface). The output signal from the distance sensor 411will be referred to as the “seed depth” signal because the depth of theopener disc determines the depth of the furrow in which the seed isplanted.

In one embodiment that provides both environmental protection and lowcost, a pair of valves are controlled to open and close to extend orretract the ram of a hydraulic cylinder to move a slider/depth adjusterto the desired position. If the position of the slider/depth adjusterfalls out of tolerance, the system automatically opens and closes thevalve to maintain the correct setting. Each row unit may be providedwith its own valves and associated control system. This design may use asmall hydraulic ram 406 to perform what would typically be a manualdepth adjustment. The ram 406 pushes on a rocker arm 404, which isconnected to a link arm 410, which is connected to a slider piece 412.The slider piece 412 is connected to the planter row unit depthadjustment handle and is free to move throughout the same adjustmentrange that the handle could be moved manually to effect a depthadjustment.

The pressure inside the chamber 408 is equivalent to the force on thegauge wheels. Thus, a single device can provide both depth adjustmentand gauge wheel force measurement, without the need for the typicalstrain gauge. The system allows fluid pressure to be used both to changethe depth that the seed is planted in the ground and how hard theplanter gauge wheels are pushing on the ground in a single device.

In the illustrative system, the fluid port 420 in the fluid chamber 408is connected to one or more valves to allow hydraulic fluid to be addedto or removed from the chamber 408 to change the angle of the openerdisc relative to the gauge wheel for any given soil condition.

The distance sensor 411 produces an output signal corresponding to theposition of the piston within the hydraulic cylinder, which changes whenthe depth of the opening disc changes relative to the elevation of thegauge wheel. For example, if the soil engaged by the opening discbecomes harder, the depth of the opening disc becomes smaller unless thedown pressure applied to the opening disc is increased. Conversely, ifthe soil engaged by the opening disc becomes softer, the depth of theopening disc becomes greater unless the down pressure applied to theopening disc is decreased. Thus, the position signal from the hydrauliccylinder actually represents the depth of the opening disc.

The small hydraulic ram 406 performs what would typically be a manualdepth adjustment. The ram 406 pushes on a rocker arm 404, which isconnected to a link arm 410, which is connected to a slider/depthadjuster 412. The slider/depth adjuster 412 is free to move through thesame adjustment range that the conventional depth adjustment handlecould be moved manually to effect a depth adjustment.

The inductive distance sensor 411 that moves closer or farther away froma metal cam target 424 as the slider/depth adjuster 412 is movedthroughout its adjustment range. The distance sensor 411 produces anoutput signal that is sent to an electronic controller that compares thesignal from the distance sensor 411 with a desired depth value enteredby the operator of the planter, as described in more detail below. Avariety of linear or angular position sensors could be used in place ofthe illustrated distance sensor, which is preferred for itsenvironmental protection and low cost.

As a controller compares the actual depth with the desired depth, itproduces an output signal that controls a pair of valves that can beopened and closed to adjust the pressure in the hydraulic cylinder thatreceives the ram 406. Changing this pressure extends or retracts the ram406 to move the slider/depth adjuster 412 to the desired position. Thus,if the position of the ram 406 falls out of tolerance, the system willautomatically open and close the valves to maintain the correct setting.

Also provided is a pressure sensor 415 that measures the pressure insidea hydraulic cylinder 408 that receives the ram 406. It can be seen thatthe force exerted on the ground by the gauge wheels is transmitted fromthe tires to the gauge wheel arms 407, both of which pivot and aresupported by the pivoting equalizer 401. This equalizer 401 is connectedto the slider/depth adjuster 412, which is connected to the link arm410, which is connected to the rocker arm 404, which in turn contactsthe ram 406, which in turn compresses the fluid in the cylinder 408,which is measured by a pressure sensor 415. Thus, the pressure insidethe cylinder 408 is equivalent to the force on the gauge wheels. In thisway, a single device accomplishes both depth adjustment and gauge wheelforce measurement, and eliminates the need for the typical strain gauge.

When planting an agricultural field with seeds, it is important tocontrol the planting depth in real time as the planting machinetraverses the field, because it is critical that the seeds all beplanted into moisture so that each seed emerges from the soil at thesame time. The depth of the seed can be changed based on some type ofmoisture sensor system, or even based on a satellite or drone systemthat is able to detect changes in the soil chemistry that would make itdesirable to change the depth of the planted seed in different areas ofthe field.

An objective of the present invention is to provide a planting systemthat enables the operator to select a desired planting depth setting,and then automatically maintains the actual planting depth within aselected range above and below the selected depth.

In one embodiment that provides both environmental protection and lowcost, a pair of valves are controlled to open and close to extend orretract the ram of a hydraulic cylinder to move a slider/depth adjusterto the desired position. If the position of the slider/depth adjusterfalls out of tolerance, the system automatically opens and closes thevalve to maintain the correct setting. Each row unit may be providedwith its own valves and associated control system.

The pressure inside the cylinder 408 is equivalent to the force on thegauge wheels. Thus, a single device can provide both depth adjustmentand gauge wheel force measurement, without the need for the typicalstrain gauge. The system allows fluid pressure to be used both to changethe depth that the seed is planted in the ground and how hard theplanter gauge wheels are pushing on the ground in a single device.

In the illustrative system, a fluid port 420 in the fluid chamber 408 isconnected to one or more valves to allow hydraulic fluid to be added toor removed from the chamber 408 to change the angle of the opener discrelative to the gauge wheel.

The distance sensor 411 produces an output signal representing theposition of the cutting wheel support arm along the arcuate slot. Thatposition changes as the angle between the two support arm changes withchanges in the depth of the opener disc relative to the elevation of thegauge wheel (the soil surface). The output signal from the distancesensor 411 will be referred to as the “seed depth” signal because thedepth of the opener disc determines the depth of the furrow in which theseed is planted.

The position sensor produces an output signal corresponding to theposition of the piston within the hydraulic cylinder, which changes whenthe depth of the opener disc changes relative to the elevation of thegauge wheel. For example, if the soil engaged by the opening discbecomes harder, the depth of the opening disc becomes smaller unless thedown pressure applied to the opening disc is increased. Conversely, ifthe soil engaged by the opening disc becomes softer, the depth of theopening disc becomes greater unless the down pressure applied to theopening disc is decreased. Thus, the position signal from the hydrauliccylinder actually represents the depth of the opening disc.

The output signal from the position sensor is supplied to thecontroller, which determines whether any change in that signal fallswithin predetermined dead bands on opposite sides of the target value.If a change exceeds a dead band, the controller produces a controlsignal that increases or decreases the down pressure on the opening discto maintain the depth of the opening disc within a desired range on bothsides of the target value.

The target value can be changed automatically as the planter traverses afield having variable soil conditions. For example, a soil moisturesensor cane be used to determine optimum target values in differentareas of a field being planted. Another example is to use stored datacorresponding to the soil properties at different GPS locations in thefield to adjust the target value as the planter traverses thoselocations.

The gauge wheel support arms 400 push against an equalizer support whichis connected to the slider/depth adjuster 412 that slides along anarcuate guide. Movement of the slider/depth adjuster 412 along thearcuate guide moves one end of the link arm 410 that is attached at itsother end to the rocker arm 404 mounted for pivoting movement abound astationary pivot pin 405. The lower end of the rocker arm 404 engagesthe ram 406 in the hydraulic cylinder 408 that is filled with apressurized hydraulic fluid.

The force on the gauge wheels due to the weight of the row unit andapplied down force causes the rocker arm 404 to pivot around the pivotbolt 405 and push against the hydraulic ram 406. This force on the ram406 controls the pressure on the fluid in the cylinder 408, so the fluidpressure in the cylinder 408 is proportional to the amount of gaugewheel load. This fluid pressure controls the depth of the opener bladeby controlling the angle between the support arms for the gauge wheeland the opener blade.

To adjust the depth of the opener blade, the pressure of the hydraulicfluid in the cylinder 408 can be adjusted by increasing or decreasingthe amount of hydraulic fluid in the cylinder. This is accomplished by apair of valves that can be opened and closed by electrical signals froman electrical controller.

The fluid cylinder 408 includes a fluid port 420 that is connected toone or more valves to allow hydraulic fluid to be added to or removedfrom the cylinder 408 to change the angle of the opener disc relative tothe gauge wheel. The distance sensor 411 produces an output signalrepresenting the position of the opener disc support arm 402 along anarcuate guide, which changes as the angle between the two support armschanges with changes in the depth of the opener disc relative to theelevation of the gauge wheel (the soil surface). The output signal fromthe distance sensor 411 can be referred to as the “seed depth” signalbecause the depth of the opener disc determines the depth of the furrowin which the seed is planted.

FIG. 34 is a flow chart of an algorithm for generating signals thatcontrol the one or more valves that control the flow of hydraulic fluidin and out of the fluid chamber 408. At step 488, this algorithmcalibrates the distance or angle sensor to read the correct seed depthin inches, and step 490 calibrates the pressure sensor 415 to read thegauge wheel force in pounds or kilograms. Step 492 computes the targetseed depth and down pressure based on the output of step 491 andexternal soil property data, furrow hardness sensor data and/or moisturesensor data. Then seed depth dead band values are entered at step 493,and down pressure dead band values are entered at step 494.

Step 500 in this algorithm determines whether the planter row unit is inan operating configuration on the ground, as will be described in detailbelow. When step 500 produces an affirmative answer, step 501 measuresthe actual seed depth, and step 502 measures the actual gauge wheelload. Steps 503 and 504 then determine whether the actual seed depth andthe actual gauge wheel load are within their respective dead bands and,if the answer is negative in either case, whether the actual value isabove or below that dead band.

In the case of the seed depth, if the actual seed depth is within thedead band, the system returns to step 500 to repeat steps 501-504. Ifthe actual seed depth is outside the dead band and is too deep, step 505opens a valve to supply additional hydraulic fluid to the cylinder 406for a brief time interval. If the actual seed depth is outside the deadband and too shallow, step 505 opens a valve to allow hydraulic fluid toflow out of the cylinder 408 for a brief time interval.

In the case of the gauge wheel load, if the actual gauge wheel load isabove the dead band, step 505 opens a valve to supply additionalhydraulic fluid to the cylinder 408. If the actual gauge wheel load isabove the dead band, step 507 decreases the down pressure actuatorpressure. If the actual gauge wheel load is below the dead band, step108 increases the down pressure actuator pressure. If the actual gaugewheel load is within the dead band, the system returns to step 500 torepeat steps 501-504.

When step 500 produces a negative answer, step 509 performs an activeair purge process, and step 510 maintains the row unit down pressure atzero for safety.

While particular embodiments and applications of the present inventionhave been illustrated and described, it is to be understood that theinvention is not limited to the precise construction and compositionsdisclosed herein and that various modifications, changes, and variationscan be apparent from the foregoing descriptions without departing fromthe spirit and scope of the invention as defined in the appended claims.

The invention claimed is:
 1. A control system for controlling the depthof an opener device in an agricultural planter, said control systemcomprising: a gauge wheel on a pivotably mounted support arm, a rockerarm coupled to said support arm to move in response to changes in theangle of said support arm, a sensor adapted to measure changes in therelative elevations of said opener device and said gauge wheel toproduce a first output signal representing the current relativeelevations of said opener device and said gauge wheel, and an electroniccontroller receiving said first output signal from said sensor andproducing a second output signal for maintaining said opener device at aselected elevation relative to said gauge wheel.
 2. The control systemof claim 1, further comprising a moisture sensor producing a signalrepresenting the moisture content of the soil being planted, saidelectronic controller being responsive to said moisture-representingsignal for producing a third output signal representing the desireddepth of said opening opener device.
 3. The control system of claim 1,wherein said sensor translates the upward force from the support arminto a fluid pressure in a fluid chamber.
 4. The control system of claim3, wherein said fluid pressure is proportional to the gauge wheel load.5. The control system of claim 3, further comprising a pressuretransducer coupled to said fluid chamber, the pressure transducerproducing a pressure signal that changes in proportion to changes insaid fluid pressure in said fluid chamber, said electronic controllerreceiving said pressure signal and using that pressure signal to producesaid second output signal.
 6. The control system of claim 1, furthercomprising a remote sensor producing a chemistry signal representing thechanges in the chemistry of the soil being planted, said electroniccontroller being responsive to said chemistry signal for producing athird output signal representing the desired depth of said openerdevice.
 7. The control system of claim 6, wherein the remote sensor is asatellite system or a drone system.
 8. A method of controlling the depthof an opener device in an agricultural planter having a gauge wheel on apivotably mounted support arm, said method comprising: in response tochanges in the angle of said support arm, moving a rocker arm coupled tosaid support arm, producing a first output signal representing thecurrent relative elevations of said opener device and said gauge wheel,in response to changes in the relative elevations of said opener deviceand said gauge wheel, and in response to said first output signal,producing a second output signal for maintaining said opener device at aselected elevation relative to said gauge wheel.
 9. The method of claim8, further comprising producing a signal representing the moisturecontent of the soil being planted, and in response to saidmoisture-representing signal, producing a third output signalrepresenting the desired depth of said opening opener device.
 10. Themethod of claim 8, wherein the upward force from the support arm istranslated into a fluid pressure in a fluid chamber.
 11. The method ofclaim 10, wherein said fluid pressure is proportional to the gauge wheelload.
 12. The method of claim 10, further comprising producing apressure signal that changes in proportion to changes in said fluidpressure in said fluid chamber, and using that output pressure signal toproduce said second output signal.